If a file descriptor to /dev/hidgN is kept open after the gadget
function has been deleted, reading or writing will block indefinitely
since no requests will ever be processed.
Add a flag to note that the function has been deleted and check this in
read & write if there is no other action to take. When setting this
flag, also wake up any readers/writers so that they get ENODEV
immediately.
Signed-off-by: John Keeping <john@xxxxxxxxxxxx>
---
drivers/usb/gadget/function/f_hid.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
index 2c3e835962a5..fdb8356e334b 100644
--- a/drivers/usb/gadget/function/f_hid.c
+++ b/drivers/usb/gadget/function/f_hid.c
@@ -59,6 +59,7 @@ struct f_hidg {
struct usb_request *req;
struct kref kref;
+ bool deleted;
int minor;
struct usb_function func;
@@ -271,10 +272,14 @@ static ssize_t f_hidg_read(struct file *file, char __user *buffer,
/* wait for at least one buffer to complete */
while (!READ_COND) {
spin_unlock_irqrestore(&hidg->read_spinlock, flags);
+ if (READ_ONCE(hidg->deleted))
+ return -ENODEV;
+
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;
- if (wait_event_interruptible(hidg->read_queue, READ_COND))
+ if (wait_event_interruptible(hidg->read_queue,
+ READ_COND || READ_ONCE(hidg->deleted)))
return -ERESTARTSYS;
spin_lock_irqsave(&hidg->read_spinlock, flags);
@@ -358,11 +363,14 @@ static ssize_t f_hidg_write(struct file *file, const char __user *buffer,
/* write queue */
while (!WRITE_COND) {
spin_unlock_irqrestore(&hidg->write_spinlock, flags);
+ if (READ_ONCE(hidg->deleted))
+ return -ENODEV;
+
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;
- if (wait_event_interruptible_exclusive(
- hidg->write_queue, WRITE_COND))
+ if (wait_event_interruptible_exclusive(hidg->write_queue,
+ WRITE_COND || READ_ONCE(hidg->deleted)))
return -ERESTARTSYS;
spin_lock_irqsave(&hidg->write_spinlock, flags);
@@ -1070,6 +1078,10 @@ static void hidg_free(struct usb_function *f)
hidg = func_to_hidg(f);
opts = container_of(f->fi, struct f_hid_opts, func_inst);
+ WRITE_ONCE(hidg->deleted, true);
+ wake_up(&hidg->read_queue);
+ wake_up(&hidg->write_queue);
+
kref_put(&hidg->kref, hidg_release);
mutex_lock(&opts->lock);
--opts->refcnt;
--
2.23.0
